Salivary Glands

The production of the vital digestion material known as saliva is attributed to the small glands called the salivary glands. Also known as accessory digestive glands, the salivary glands are in charge of two functions. First, it breaks down the molecular structure of the food, thereby lending taste to it. And, it cleans the teeth and maintains the moisture of the mucous membranes inside the mouth. Saliva is necessary to digestion because it contains two enzymes important to digestion and swallowing - starch-digesting enzymes and a lubricating enzyme. Though the production of saliva is constant and continuous, it nevertheless is produced in amounts that are only enough to keep the mouth moisturized when a person is not eating. A normal person secretes 1 to 1.5 liters of saliva in one day.

The mucous membranes of the palatal area house a lot of minor salivary glands. The greater amount of saliva produced is supplied by three pairs of glands outside the oral cavity. The saliva from these glands is admitted to the mouth through the ducts that connect to the oral cavity. These three glands are the parotid, the submandibular and the sublingual. The largest of these is the parotid.

The parotid gland is situated in between the skin and the masseter muscle, underneath the auricle of the ear. The saliva from this gland enters the oral cavity by way of the Stensen’s duct, also known as the parotid duct. The parotid duct follows the same path as the zygomatic arch until runs into the masseter muscle, crosses into the buccinator muscle until it reaches the second upper molar. At this point, the parotid duct delivers the saliva into the mouth. In case of mumps, the parotid gland is the one that swells.

The second main salivary gland, the submandibular gland, is located under the mandible, near the interior of the jaw. Superficial protection to the gland is provided by the mylohyoid muscle. Saliva produced by this gland enters the oral cavity through the submandibular duct (also known as the Wharton’s duct), parallel to the lingual frenulum. Several ducts that transport the saliva into the oral cavity line along the sublingual glands, which are referred to as the Rivinus’ ducts or the sublingual ducts. These ducts deposit the saliva behind the papilla of the submandibular duct.

Secretory cells in the body are of two types. Both are found in every salivary gland, but the amount of the two vary. Serous cells, one of the two types, produce secretions that contain the same liquid quality as water, only with an enzyme for digestion. Mucous cells, the other type, produce secretions that are more viscous and thick. All salivary ducts’ lumina is covered with cuboidal epithelial cells. The salivary glands are controlled by the two divisions of the autonomic nervous system. Viscous saliva is released by stimulating the sympathetic impulses. The watery saliva from the serous cells is triggered by the parasympathetic impulses. Salivating when thinking, smelling, tasting, or dreaming about food is stoked by a physiological response to the stimulation of the parasympathetic impulses.